Extreme Temperature Diary- Monday November 2nd, 2026/Main Topic: Volcanic Eruptions in the Tropics Are a Major Factor in Earth’s Thermostat

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Episode: 10/29/2026 — More info…

Volcanic eruptions in the tropics are a major factor in Earth’s thermostat

November 2, 2026 feature

Volcanic eruptions in the tropics are a major factor in Earth’s thermostat

by Hannah Bird, Phys.org

edited by Sadie Harley, reviewed by Robert Egan

Volcanic eruptions lead to aerosol formation in the atmosphere that can block sunlight and cool the planet. Credit: Diego Girón/Pexels.

Volcanic eruptions are known for their spectacular visual displays of vivid lava, as well as the devastating impacts they can have on the environment and the communities who live nearby. But they can also have far-reaching impacts across the globe.

Explosive eruptions release vast quantities of sulfur dioxide gas into the upper atmosphere (stratosphere), where it reacts with water vapor and oxygen to form tiny aerosol droplets of sulfuric acid. These droplets scatter and reflect incoming solar radiation from the sun back out to space, reducing the warming energy reaching Earth’s surface and therefore helping to keep the planet cooler for multiple months or even years.

A famous example of this is when Mount Tambora in Indonesia erupted in 1815, leading to the “year without a summer” in 1816. Mary Shelley spent much of that time indoors due to the poor weather and wrote the literary classic “Frankenstein” in Switzerland and England—a curious cultural connection to a seemingly unrelated event far away.

New research, published in Geophysical Research Letters, has now explored whether a volcano’s location makes a difference in the amount of cooling experienced in the Northern Hemisphere.

A cooling conundrum

Dr. Zachary McGraw, of Columbia University, and colleagues report that previous studies have found volcanic eruptions in the middle latitudes between 30° and 70° (known as the extratropics) produced greater cooling than tropical eruptions of similar magnitude.

To test this, the researchers used a NASA climate model to simulate the difference between tropical and extratropical eruptions that released different amounts of sulfur gas across eruptions in summer and winter.

However, the team found no clear indication of increased Northern Hemisphere cooling based on an erupting volcano’s location—at most, an extratropical eruption increased cooling by twice as much, not the 7.5 times found in previous studies.

They identified that there could be some enhanced cooling from extratropical eruptions as a result of the microscopic aerosols being concentrated within just the Northern Hemisphere, whereas aerosols from tropical eruptions are moved into both hemispheres by wind patterns to distribute the reflective cooling effects of aerosols more evenly. This is the only mechanism that they say could create increased cooling in the extratropics, and there is no known process that could amplify cooling to 7.5 times.

To consider this in real terms, McGraw and the team tested this theory against ancient climate records to see how past tropical and extratropical eruptions had influenced weather. One of these so-called paleoclimate proxies is tree rings. The annual growth rings of trees can become wider during wet or warm seasons and narrower during dry or cold years when they’re experiencing more environmental stress.

They therefore considered tree ring data associated with historical records of extratropical eruptions from 1783 CE in Iceland, 536 CE somewhere in the mid-latitudes and 43 BCE in Alaska, as well as simulating 100,000 similar eruptions and subsequent cooling periods due to a lack of modern extratropical eruptions.

This was compared to numerous post-750 CE tropical eruptions to identify patterns in weather following an eruption and validate whether modeling can accurately represent climate patterns seen in historical records.

In doing so, the researchers found that Northern Hemisphere cooling coincides more often with tropical eruptions and that extratropical eruptions are comparatively rarer, so have a smaller influence on temperatures in the Northern Hemisphere.

They also identified shorter aerosol lifespans for extratropical eruptions (often up to nine months) compared to tropical eruptions (up to three years). They attributed this to sulfur gases being released into the atmosphere at lower heights, aerosols being washed away by rain and snow due to the wetter and cooler climates, and the poleward transport of aerosols from mid-latitudes.

The bigger picture

Disputing the cooling power of extratropical eruptions helps scientists explore the temporary effects of eruptions alongside longer-term trends in climate that are driven by other factors, such as human-made greenhouse gas emissions.

This study has important implications for understanding the risks posed to society. With tropical eruptions remaining the dominant driver of cooling in the Northern Hemisphere, scientists can use this knowledge to model how aerosols can be distributed across the planet, assess potential issues for agricultural production and global food security and the risk of conflicts over resources leading to geopolitical instability, and make meaningful plans to tackle climate risks.

Written for you by our author Hannah Bird, edited by Sadie Harley, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You’ll get an ad-free account as a thank-you.

Publication details

McGraw et al., No evidence for strongly enhanced Northern Hemisphere cooling from extratropical versus tropical eruptions, Geophysical Research Letters (2026). DOI: 10.1029/2026GL122071

Journal information: Geophysical Research Letters

Key concepts

climatologyvolcanic activity

Who’s behind this story?

Hannah Bird

PhD Earth Sciences in oceanography and paleontology. 10+ years translating complex science for mainstream media audiences. Full profile →

Sadie Harley

BSc Life Sciences & Ecology. Microbiology lab background with pharmaceutical news experience in oil, gas, and renewable industries. Full profile →

Robert Egan

Bachelor’s in mathematical biology, Master’s in creative writing. Well-traveled with unique perspectives on science and language. Full profile →

U.S. records for November 1, 2026, part 2.

— Don Sutherland (@donsutherland1.bsky.social) 2026-11-02T11:25:31.487Z

U.S. records for November 1, 2026, part 3.

— Don Sutherland (@donsutherland1.bsky.social) 2026-11-02T11:26:53.470Z

Canadian records for November 1, 2026. #Canada

— Don Sutherland (@donsutherland1.bsky.social) 2026-11-02T11:08:36.481Z

October 2026 was the warmest October on record. That is all. 🔥

— Climatologist49 (@climatologist49.bsky.social) 2026-11-02T16:04:34.633Z

The preliminary global mean surface temperature for October 31 was 14.980C. That would break the daily mark of 14.831C from 2024. October 2026 finished as the warmest October on record. #ClimateChange

— Don Sutherland (@donsutherland1.bsky.social) 2026-11-02T11:02:01.952Z

Following the record warm October, 2026 ranks as the second warmest year on record (ERA-5). #ClimateChange

— Don Sutherland (@donsutherland1.bsky.social) 2026-11-02T11:03:06.887Z

Here is the January-October 2026 temperature ranking compared to all January-October periods since 1895 using PRISM data. Nationwide, it is easily the warmest January-October on record. 🔥🔥🔥

— Climatologist49 (@climatologist49.bsky.social) 2026-11-01T15:37:34.655Z

Earth has never had a month that exceeded +2C above pre-industrial. But that may change by winter. 1/2 of the Super Ensemble members forecast a +2C month – the average says we reached +2C is February. BOM is the highest at +2.33C. This breach of 2C is due to global warming, with the Super El Niño…

— Jeff Berardelli (@weatherprof.bsky.social) 2026-10-31T18:33:52.023Z

New reports show overshooting 1.5C will have devastating impacts on ice sheets, glaciers, permafrost,sea ice, polar oceans, with deadly repercussions around the globe.iceblog.org/2026/11/02/a…

— Irene Quaile (@iceblogger.bsky.social) 2026-11-02T08:06:19.872Z

Once again – and in classic El Niño fashion – torrential rains are soaking the U.S. Sunbelt. Multiple rivers in the Southwest have set record crests, and Melbourne, FL, is having its wettest day on record. Full report with @drjeffmasters.bsky.social:yaleclimateconnections.org/2026/11/colo…

— Bob Henson (@bhensonweather.bsky.social) 2026-11-02T19:25:58.728Z

As of Monday morning, 10 flood gauges in Arizona, CO & NM had set new height records. The Gila River near Solomon, AZ broke its 112-year by over 6 ft.The San Juan River at Shiprock, AZ set a 98-year high, besting the previous record by nearly 5 ft. Story: www.accuweather.com/en/weather-n…

— WeatherMatrix (@weathermatrix.bsky.social) 2026-11-02T19:00:20.140Z

Incredible: wettest day on record for Melbourne FL. Observations there go back 89 years (to 1937).

— Bob Henson (@bhensonweather.bsky.social) 2026-11-02T18:48:32.902Z

#Melbourne, FL has received 10.28” (261.1 mm) of rain so far today. That breaks the daily record of 1.64” (41.7 mm) from 2008, monthly mark of 5.45” (138.4 mm) from November 29, 1977, and all-time daily record of 10.23” (259.8 mm) from September 10, 2017. #flwx #deluge

— Don Sutherland (@donsutherland1.bsky.social) 2026-11-02T17:41:46.033Z

And the flooding in Florida where we have another 20” in 6 hour rain bomb near Palm Bay. Gauge has measured about a foot of rain in last 24 hr at Melbourne Int’l north of heaviest rainfall. Flash flood emergency in effect as storms continue to stream west off the Atlantic. #flwx

— Alan Gerard (@wxmanms1.bsky.social) 2026-11-02T17:44:36.842Z

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